PURPOSE: To evaluate the effect of the hyperhomocysteinemia on pregnancy rate, implantation rate and abortion rate after IVF.METHOD: Data from a total of 48 infertile couples with hyperhomocysteinemia were prospectively collected for this study. All patients underwent a standard down regulation protocol for ovarian stimulation. Oocytes recovery was performed at 36 h after hCG administration. Embryo transfer took place at 48 h after insemination. The patients were matched in two groups that received or did not receive therapy (group A and B respectively) to normalize homocysteine plasma level.RESULTS: Pregnancy rate, implantation rate and abortion rate varied significantly (p<or=0.05) between the two groups. The number and quality of embryos transferred did not differ between the groups.CONCLUSION: The results suggest that hyperhomocysteinemia could affect IVF outcome.